Method and apparatus for manufacturing expanded structural members and its products

ABSTRACT

This invention relates to a method of manufacturing expanded structural members from metal strip through a roll forming process, a slitting process, a horizontally expanding process with small rollers by rolling, a V-shape expanding process, a recovering process, a levelling process, a reshaping process and/or reinforcing process. All the processes comprising only rotary motion with cold working. The lattice part of the member is elongated and slackened by rolling with small rollers, at the same time, the part is naturally expanded horizontally. In the Vshape expanding process, the strip sheet or shape is guided by the edges of the respective V-shape rollers without using guide bars, while the lattice part is expanded between the respective rollers. The lattice part is, in turn, rolled by the respective V-shape rollers and expanded by gradually being bent into a Vshape by the V-shape rollers, and in the final reinforcing process, the lattice part is reinforced by dottedly convex rollers meshing with each other in bead form.

United States Patent [1 1 Watanabe [111 3,812,558 [451 May28, 1974 METHOD AND APPARATUS FOR MANUFACTURING EXPANDED STRUCTURAL MEMBERS AND ITS PRODUCTS [76] Inventor: Hideyo Watanabe, No. 1-10-11 Higashi-gotanda, lchome, Shinagawa-ku, Tokyo, Japan [22] Filed: Apr. 30, I971 [21] Appl. No.: 139,077

[30] Foreign Application Priority Data Apr. 30, 1970 Japan 45-36413 [52] US. Cl. 29/6.] [51] Int. Cl. B2Id 31/04 [58] Field of Search 29/6.l

[56] References Cited UNITED STATES PATENTS 1,052,888 2/1913 Clark 29/61 1,747,138 2/1930 Kessler 29/61 1,827,314 10/1931 Gersman 29/6.1 1,949,966 3/1934 Kessler 29/6.1 3,034,197 5/1962 Watanabe 29/6.1

Primary ExaminerAndrew R. Juhasz Assistant ExaminerLeon Gilden Attorney, Agent, or Firm-Sughrue, Rothwell, Mion,

Zinn & Macpeak [57] ABSTRACT This invention relates to a method of manufacturing expanded structural members from metal strip through a roll forming process, a slitting process, a horizontally expanding process with small rollers by rolling, a V-shape expanding process, a recovering process, a levelling process, a reshaping process and- /or reinforcing process. All the processes comprising only rotary motion with cold working. The lattice part of the member is elongated and slackened by rolling with small rollers, at the same time, the part is naturally expanded horizontally. In the V-shape expanding process, the strip sheet or shape is guided by the edges of the respective V-shape rollers without using guide bars, while the lattice part is expanded between the respective rollers. The lattice part is, in turn, rolled by the respective V-shape rollers and expanded by gradually being bent into a V-shape by the V-shape rollers, and in the final reinforcing process, the lattice part is reinforced by dottedly convex rollers meshing with each other in bead form.

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BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method and apparatus for manufacturing expanded structural members and its products, and more particularly to an expanded structural member having superior dynamic characteristics and capable of various shapes and utility, while produced from metal strip or shape by continuous and high speed cold roll-working.

2. Description of the Prior Art Heretofore, expanded structural members have been manufactured by hot working, for example, Bethlehem Steel Co., National Steel Corp., Jones and Laughlin Steel Corp., and other major steel producers have used this method for forty years.

Recently, expanded structural members have been manufactured by other methods by reason of the development of automatic welding and the comparative inefficiency of hot working with products obtained thereby having bad dynamic characteristics.

After much experimentation, I started searching the possibility of manufacturing expanded structural members with cold working. In the initial stages, after providing slits on the web of a channel, I tried to expand both flanges of the channel by such methods as hot working. But, tension acting on the lattice part, with a consequent compression, acted on both flanges and caused cracks at the root of the lattice part. Moreover, this approach contained other disadvantages.

On the other hand, when only the lattice part was elongated skillfully by hammering or rolling, I found that the lattice part might easily be expanded without applying compression force to the flange portion. I understood that to mechanize this idea was the correct way for developing the manufacture of the expanded structural member industrially in cold working.

Under this idea, I invented my first manufacturing method, Japanese Pat. No. 258,323, of expanded structural members in cold roll-working wherein the method had the processes of roll-forming the material into channel, alternately slitting the web of the channel rollforming to provide a lattice part thereon, and rolling the lattice part over while guiding both flanges by guide bars set along both sides of rollers in taper.

By this method, the lattice part was gradually expanded by the guide bars while the part was constantly rolled.

This method succeeded beyond my expectations, that is, where a metal strip made up of SPHl of the Japanese Industrial Standards was, used as the material, cracks which normally occur at the root of the lattice did not occur if the lattice angle was 22 or less.

But, in the expanded structural members manufac- 2 any kind of strip steel has an irregularity of thickness and hardness in one coil. As a result, even if the rolling reduction was previously adjusted correctly, sometimes the lattice was excessively expanded, in this case, and slackness occured in the product. Sometimes the lattice was not sufficiently expanded, and in this case, a crack occured at the root of the lattice. Where the rolling reduction of the material was less than 2-3 percent in every roll-stands, this problem was due to the standard of the strip steel material of shape,

Eventually I understood that using the aforesaid first method, it was impossible to commercially manufacture expanded structural members.

After I had investigated this matter, I invented a further improved method which overcame the aforesaid disadvantageof the first method. As an advantage of this second method, the respective expanding rollers were formed so as to always elongate the lattice element slightly in excess, by the respective rollers, of the amount of elongation required to expand the lattice part at the respective roll-stands. By this method, therefore, the lattice element was made to constantly slacken between the respective roll-stands. And then, the slackened lattice element was recovered by several levelling rollers disposed behind the final expanding rollers for producing the flat shape. (US. Pat. No. 3,034,197 corresponding to Japanese Pat. No. 260,232).

According to this second method, any variation of the thickness of the commercial metal strip was absorbed in the variation of the slackness of the lattice, so that the shape of the lattice became S-shaped in the thicker portion than the mean thickness of the metal strip, on the other hand, in the thin portion, the lattice shape became straight. By this method, it was possible to manufacture expanded structural members commercially with cold roll-working without producing a crack at a root of a lattice element and the original bend of the lattice element.

However, while producing about 10,000 tons expanded structural members of 200mm in width from the strip steel ofSPI-Il of 1.0-4.5 mm in thickness by the second method as aforesaid, I discovered thefollowing matters:

1. By using the guide bars for expanding the lattice part, it is impossible to increase the production speed over 20 m./min., because, if the production speed is over 20 m./min., the material and bars seize by the friction therebetween. And further, the operation becomes unstable when the guide bars are worn. As the result of this, the accuracy of the product tends to be lowered.

2. If SPHI haying agoodductibility in the Japanese lndiistrial Standards is used as the material, the lattice elements may be formed at an angle of approximately 30 from the side lines of both flanges, but if SS41(J IS) having poorer ductibility and higher tensile strength than that is used as the material, the angle becomes more or less 22, and if the angle is increased more than that, a crack occurs at the root of the lattice part or the lattice will be broken. As the result of this, the product has bad dynamic characteristics and has an improper shape for a structural member.

3. The respective expanding rollers also feed the material. But, in the second method using guide bars, the respective expanding rollers must provide the material with an excessive feeding force in order to overcome any resistance which is produced by the friction of the material and the guide bars. This is one factor for causing the crack at the root of the lattice element.

4. When the expanded structural members are cut in the final process, it is necessary that the lattice and both flanges always contact at that cut end portion. And, moreover, even if the product is cut in any length, the lattice pitch therein must always be even.

While the second method enabled the manufacture of such products as a finishing member, it was still insufficient to manufacture the product as a structural member.

I then executed a production test by producing hat type expanded structural members in order to solve the first problem of the aforesaid four problems of the second method.

In this test, both sides of the hat shape rollers were so designed as to adapt the guide of the flange portion of the channel instead of the guide bars, and each hat shape roller might feed the channel in the state that two lines formed by both corners of the bend portion in both flanges are always held in parallel, at the same time, the lattice part was pressed to be bent in hat shape (J1) so as to advance to roll, which was the third manufacturing method (Japanese Pat. No. 448,796). As a result, even if the production speed was increased to approximately 50m/min., seizure did not occur. The first problem was'solved by applying this method tothe other shape of expanded member.

This invention is to provide expanded structural members which are adapted for broad usage and have sufficient function in strength, quality and shape, by solving other problems and disadvantages and incompleteness of the aforesaid second method.

SUMMARY OF THE INVENTION Generally speaking, in order to provide expanded structural members with sufficient function and utility as a structural member, the shearing strength of the lattice part should balance with the bending rigidity, and, in its quality, it is required to have at least 4lkg/mm or more of tensile strength in Japan, and to perform this purpose the lattice should be formed at an angle of at least preferably or more, from the side lines of both flanges.

A product whose thickness is relatively thick as compared with the size of it may sufficiently satisfy the aforementioned conditions, but in the case of the product where the thickness is relatively thin, buckling occurs at the lattice part even if it has a lattice angle of 30 or more and the material is over 4lkg/mm of tensile strength.

Then, in this case, the member is insufficient as a structural member. Therefore, the lattice part of. the product whose thickness is thin must be reinforced by some manner in order to increase the shearing strength thereof.

This invention has succeeded in reinforcing the lattice part by deforming the lattice element into a bead shape without sacrificing productivity. As the result of this, the moment ofinertia, shearing strength and maximum breaking load of the lattice part are increased. On the other hand, after detailed investigation of the generation of a crack produced at the root of the lattice part in the old manufacturing process, I found that an initial small crack will occur immediately after the slitting of the lattice part of the material and this crack will increase gradually in a V-shape expanding process.

The present invention has succeeded in preventing the occurrence of the initial crack and the growth of such a crack.

The present invention has a unit comprising a group of small pair rollers whereby the lattice part is gradually and naturally expanded so as not to generate a crack at the root of each lattice element. The reason why the unit can provide the lattice element with the above described effect is that the lattice element is made to constantly slacken between the respective small rollers of the unit so as to always generate the compression force in the longitudinal direction thereto by the action of the unit and also, at the same time, the aforesaid effect of the Rolling Lateral Bending Phenomenon works effectively on the lattice element by rolling the element slightly with the small pair of rollers. The unit is disposed just behind the slitting rollers. In addition, the Rolling Lateral Bending Phenomenon works particularly effectively on material of SS41.

Accordingly, the present invention may form the lattice angle of at least 25 or more without producing cracks at the root of the lattice element with even SS4] steel having high hardness and less ductibility.

As a result of this, the present invention is capable of producing expanded structural members having supe- 1 rior dynamic characteristics in cold roll-working.

In addition, this invention utilizes a slitting device in which the rotating speed of the top slitting roller is continuously and positively changeable with respect to the rotating speed of the bottom slitter roller which almost follows the feeding speed of the material. Accordingly, the length of slits may be adjustable, so that the lattice pitch may be varied optionally. It is, therefore, possible to manufacture an expanded structural member having an even lattice pitch in any length. Furthermore, it is also possible to cut the product having the even lattice pitch in any length by the combination of the aforesaid lattice cutting means, the cutting dies, the pitch counter device interlocked thereto, the clutch mounted to the slitting device, the rack device, etc.

Thus, my investigation on expanded structural members started from the similar method of hot working process, but, through changing a fundamental idea, I reached the first method called Guide Bar Method (Japanese Pat. No. 258323). This method was the basic concept of the cold roll-working connecting with the present invention, but, this method was only the initial experimental step.

Thereafter I invented the second method (U.S. Pat. No. 3,034,197 corresponding to Japanese Pat. No. 260232) wherein the method could industrially produce expanded'structural members from a commercial strip steel coil by combining levelling rollers for eliminating a slack of a lattice element.

The present invention not only provides a manufacturing method having high productivity and excellent stability of exapanded structural members, but also produces expanded structural members having various shapes such as channel type, C type, hat type, 2 type, Z type, H type, etc., and having superior dynamic characteristics. The present invention has a horizontal expanding small rollers unit disposed just behind the slitting rollers which can provide effectively the lattice element with the Rolling Lateral Bending Phenomenon.

In the case of a product whose thickness is relatively thin as compared with its size, reinforcing rollers meshed with dottedly convexities, are formed on the surface thereof, and are disposed behind the reshaping rollers as the final process of this invention.

As the result of this, expanded structural members whose thicknesses are relatively thin as compared with their size, have sufficient dynamic characteristics for a structural member.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B are elevational views of essential parts of an apparatus for performing the method of the present invention;

FIGS. 2A and 2B are a series of transverse vertical sectional views of the essential parts of FIGS. 1A and 1B, co-ordinated with FIGS. 1A and 18;

FIGS. 3A and 3B are plan views of an expanded structural member during formation by the apparatus of F [C this plan view being coordinated with the elevational views of FIGS. 1A and 18;

FIGS. 4, 5, and 6 are enlarged sectional views of three sets of V-shape rollers whereby a lattice part is made to gradually expand;

FIG. 7 is a developed plan view of the surface of the reinforcing rollers having dottedly convexities whereby a lattice element is formed into bead shape in order to reinforce the lattice part;

FIG. 8 is a partial transverse vertical sectional view through a pair of reinforcing rollers illustrating the operation thereof in deforming beads to the lattice element;

FIG. 9 is an elevational sectional view coordinated with FIG. 8',

FIG. 10 is a partial perspective view of the lattice element deformed into bead shape;

FIG. 11A is an enlarged sectional view of the deformed lattice elements divided into five stages from the case of a central mound shape to the case ofa symmetry wavy shape;

FIG. IIB is a graph for comparing the results of strength tests of the deformed lattice element pieces illustrated No. 2 to No. 6 in FIG. 11A with the result ofthe same strength test of the flat lattice element illustrated No. l in FIG. 11A, the strength tests being tested by a central concentrate loading method;

FIG. 12A is a plan view of one embodiment of the expanded structural member of the present invention in channel type;

FIG. 12B is a sectional view along the line XIIB-X- IIB in FIG. 12A;

FIG. 13A is a plan view of the expanded structural member of channel type obtained by the manufacturing method of US. Pat. No. 3,034,197;

FIG. 13B is a sectional view along the line XIIIB-X- IIIB in FIG. 13A;

FIG. 14 is a graph for comparing the result of strength tests of the present expanded structural member illustrated in FIGS. 12A and 12B with the result of strength test ofthe conventional one illustrated in FIGS. 13A and 138, both members being tested by the central concentrate loading method as shown in FIG. 14;

FIG. 15 is a sectional view of the shape of the test piece used in the aforementioned strength test;

FIG. 16 is a plan view of the comparison by the same photograph of the products (e) manufactured by the US. Pat. No. 3,034,l97 and the product 0) of the present invention shown in FIGS. 12A and 12B;

FIGS. 17A, 17B and 17C are photographs of the present channel type products having the respective lattice angles corresponding to the respective lattice pitches;

FIGS. 18 and 20 are a plan and a sectional view of other embodiments of the C type product reinforced on the lattice portion which are obtained by the manufac-' turing method of the present invention;

FIG. 19 is a graph for comparing the result of the strength test of the product illustrated in FIG. 18 with the result of the strength test of the same product except that its lattice part is not reinforced, the members being tested by the center concentrate loading method with an Anslar testing machine;

FIG. 21 is a graph for comparing the result of the strength test of the-product illustrated in FIG. 20 with the result of the strength test of the same product except that its lattice part is not reinforced, the members being tested by the same method as FIG. 19;

FIG. 22 is a sectional view of the shape of the test pieces used in the above strength tests which are nested in a box shape;

FIG. 23A is a photograph showing the test state in maximum loading to the test piece in shape shown in FIG. 22 of the product shown in FIG. 20;

FIG. 23B is a photograph of the same state of the same product shown in FIG. 18, except that it is not reinforced;

FIGS. 24A and 24B are photographs of the same state of the same product shown in FIG. 20, except that it is not reinforced;

FIG. 25A is a photograph showing the products of channel type, H type and Z type of the products obtained by the present invention; and

FIG. 25B is a sectional view of the products of the aforesaid types.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Generally speaking, in order that the expanded member may have sufficient function and broad utility as a structural member, it is desirable that the shearing strength force of the lattice part must balance with the bending rigidity and it must have at least 4lkg/mm or more tensile strength, with the lattice forming an angle of at least 25, preferably 30 or more, from the side line of the flanges of both sides.

A product that is relatively thick as compared with its size, will sufficiently satisfy the above-mentioned conditions, but a product whose thickness is relatively then won't, since buckling occurs at the lattice part even if the product has a lattice angle of 30 or more and the material used has over 4lkg/mm of tensile strength. For this reason, in such a thin product, the lattice part must be reinforced so as to increase the shearing strength force of the member.

It is, therefore, one object of the present invention to provide a method of manufacturing expanded structural members which have various utility and superior dynamic characteristics.

It is another object of the present invention to provide a method of manufacturing expanded structural members continuously and in higher speed under stable operation in cold working.

It is a further object of this invention to provide a method of manufacturing expanded structural members in high yield and economically.

It is still another object of the invention to provide a method of manufacturing expanded structural members with commercial strip steel or shape.

It is still another object of the invention to provide a method of manufacturing expanded structural members with a roller mechanism which is composed of rotary motion only through the production stages.

It is still another object of the invention to provide a method of manufacturing expanded structural members having the lattice element being formed at an angle of at least 25, preferably 30 or more, from the side lines of flanges without producing defects, such as cracks.

It is still another object of the invention to provide a method of manufacturing expanded structural members having always an even lattice'pitch in any required length.

It is still another object of the invention to provide a method of manufacturing an expanded structural member which may be cut, the expanded structural members having an even lattice pitch and the lattice elements fixed on flanges at that cut portion.

For performing the aforesaid objects of this invention, this invention provides a method and apparatus for manufacturing expanded structural members from metal strip sheet or shape by a rolling mechanism, which is composed of only rotary motion, comprising:

a. a roll forming process for forming a material to the required shape for the following processes,

1). a slitting process for alternately providing the web portion of said material with slits by a slitter comprising roll'cutter means,

c. a horizontal expanding process for naturally expanding a lattice part by rolling only the web portion at more than two positions within one pitch of each slit thereof with small rollers without drive to the required amount of expansion for the next V-shape expanding process, while slackening a lattice element between the small rollers in order to constantly provide a compression force to the lattice element in the longitudinal direction thereof and also, at the same time, for elongating the lattice element slightly in excess of the required amount of elongation for the next V-shape expanding process,

d. a V-shape expanding process for guiding both flanges of each side of the material and both ends of respective V-shape rollers while keeping each corner of both bent portions of both flanges in parallel through this process, while at the same time, gradually bending the lattice part into a V-shape to expand the part by the respective V-shape rollers while slackening the lattice element between each V-shape roller similar to the former process I e. a recovering process for returning the lattice part bent into a V'-shap'e by the former process (d) to a flat state, f. a levelling process for removing the residual slack of the lattice element to make it stable with the flat state by a series of small rollers disposed in zigzag with respect to the situation between the top and bottom rollers, and

g. a reshaping process for finishing the shape of each part of the product, which has already a desired shape as an expanded structural member, obtained by the afore-mentioned processes.

h. a reinforcing process for deforming the lattice element into a bead shape to reinforce the lattice part, the rollers having dottedly convexities on the surface thereof in which the convexities are aligned along approximately the lattice angle.

This invention further provides a slitting device comprising a special mechanism, that is, the rotating speed of the top slitting roller may be continuously and positively changeable relative to the rotating speed of the bottom slitting roller which almost follows the feeding speed of the material. By this mechanism, the length of slits formed on the web portion of the flanged material may be adjustable, so that the lattice pitch may be varied optionally. It is, therefore, possible to manufacture expanded structural members having an even lattice pitch within any desired length.

Furthermore, it is possible to cut the product having an even lattice pitch within any desired length by combining the aforesaid mechanism with cutting dies, pitch counter device interlocking the slitter, clutch mounted to the slitting device and rack device, etc.

Reference is nowmade to FIGS. 1A and 1B, which show one embodiment of the method'and apparatus of this invention for the working process for manufacturing expanded structural members.

The initial step starts with the formation of the flanges l'at each side of the material. The forming process is performed by a series of several pairs of rolls l2, 13, Hand 15. Slitting rollers 15 have cutters 7, 8 and 8, which form slits 5, 6 and 6 in order to form lattice 2 in the web of material 4. Behind the slitting rollers 15, is a horizontal expandingunit comprising a series of small rollers so closely'disposed. as .to roll at least two positions within one pitch (p) of the slits. The diameter of each roller is smaller than half of the length of a slit. The lattice part 2 is rolled by the small rollers unit 9 with constant slackening between the respective small rollers so as to always generate a compression force in the longitudinal direction of the lattice. Accordingly, the lattice part is gradually, horizontally and naturally expanded, and then, the lattice part is further expanded by gradually bending it into a V-shape with the respective V-shape rollers 16, 17 and 18, the desired V-shape being slackened constantly similar to the former process. Each of these V-shape rollers has clearances for making the non-pressure portion on the flange part 1, so as to roll only the lattice part as shown in FIGS. 4, 5 and 6. The V-shape rollers guide both flanges ateach side thereof so as to always hold them in parallel, while at the same time, the material is fed by both edges of the rollers. Then, the lattice part is expandedto the desired V-shape similar to the rollers in shape, but it is reworked by the shallow V-shape rollers. 19 into an almost flat state having the desired flange width, and finally, the lattice part is made flat bylevelling rollers 20. Then, the material 4 is finished to the desired shape as the structural member by the finishing rollers-21 and 22. In those cases where the product thickness is relatively thinas compared with its size, lattice reinforcing rollers 11, 11, which superficially resemble embossing rollers, but on close examination are different, are employed, after finishing rollers 22, as the final process of this invention in order to reinforce the lattice part. To describe the rollers in detail with reference to FIGS. 7, 8 and 9, the lattice reinforcing rollers 11, ll of top and bottom rotate, over meshing each other with each convexity l and leaving the space of the thickness of the material between their surfaces and top of respective convexities of the rollers. Each convexity has a diamond shape at its bottom and a mound shape at its top formed on the surfaces of each roller.

The lattice part 2 inserted into the lattice reinforcing rollers 11, 11 is continuously deformed into a bead form by rotation of the rollers as shown in FIGS. 8 and 9. The lattice part 2 is held in position as shown with dotted line in FIG. 7, namely, both side portions of the lattice are continuously pressed downwards by the convexities 10b, 10b of top roller of the lattice reinforcing rollers so that the portions are bent. At this time, an intermediate portion of the lattice is continuously supported by the convexity 10a as shown in FIGS. 8 and 9. Thus, the lattice element is made to deform into the shape shown in FIG. 10 by the lattice reinforcing rollers 11, 11. As the result of this, it becomes possible to reinforce the lattice part without sacrificing the productivity of the product. The reason why the lattice element is deformed as shown in FIG. 10 is clear, since the lattice element is deformed easily in the longitudinal direction thereof, while on the other hand, it is difficult vto deform in the lateral direction thereof. As shown in FIG. 10, the line of beads 3 on the intermediate portion of the lattice element is seen as a small protrusion microscopically, but seems like a continuous wavy line along the longitudinal direction of the lattice element, which is reinforced effectively.

It should be understood from the foregoing description that the web of the material slitted by slitting rollers is expanded by the horizontal expanding small rollers 9 disposed just behind the slitting rollers 15 so as to prevent the occurrence of any initial cracks, which can exert a bad influence on the expanded structural member, on the other hand, even if any initial cracks should occur because of using less ductile material, the growth of the crack is prevented in advance of the expanding action. The reason for this is that the re spective rollers have diameters less than half of the length of the slit so as to roll at more than two positions within one pitch (p) of the slits proviced on the web of the material and yet are closely disposed and the lattice element is slackened between the respective small rollers to be rolled so as to generate a compression force always in the longitudinal direction of the lattice element and the aforesaid Rolling Lateral Bending Phenomenon" effectively thereon. For this reason, the rolling and horizontal expanding unit composed of small rollers 9 corresponds to the width of the flanges of the material at the respective stage of the top rollers as shown in FIG. 2A, but the bottom rollers are so formed as to always roll only the lattice part of the material at the respective stages, and yet are combined with a series of small rollers having diameters less than half of the length of the slit.

In the conventional method, the lattice part is horizontally expanded by being guided in a tapered state with guide bars, which are disposed along the respective expanding rollers, over rolling through the expanding process.

Thus, the lattice part has been expanded in the lateral direction of the material by guiding the flanges horizontally through the process with the above-described guide bars.

As the result of this, when the working speed is over 20m per minute, the contacting portions of the flange and guide bars seize due to friction therebetween so that the working speed cannot be increased. Moreover, because the feed of the material becomes unstable due to the wear of the guide bars, the accuracy of the product tends to be lowered. As compared with the aforesaid conventional method, in the present invention, the material is guided and expanded by both edges of the respective V-shape expanding rollers in the expanding process while at the same time, the material is fed uniformly by the respective rollers in a stable operation so the manufacturing working speed may be increased to m per minute or more.

In addition, according to this invention, the rotating speed of the top slitting roller may be changeable positively and continuously relative to the rotating speed of the bottom slitting roller almost following the feeding speed of the material in the slitting process. By this mechanism, the length of the slit may be adjusted. As the result of this, the expanded structural members may be always formed into an even lattice pitch within any required length and, accordingly, the aforesaid expanded structural members having even lattice pitches within any required length may always be cut to the length by combining the cutting means with the cutting dies, the pitch counter device interlocking to the top slitting roller, the clutch mounted to the slitting stand and rack device, etc., at the root position of the lattice element and both flanges.

Moreover, according to the present invention, since the expanded structural members obtained from thin materials have weak shearing strength in the lattice part and accordingly, have unbalanced dynamic characteristics, it is necessary to reinforce the lattice part. According to the present invention, the lattice part may be reinforced by deforming the lattice element into a bead shape with the aforesaid special dottedly convex rollers without sacrificing productivity.

According to the method of the present invention, since the lattice reinforcing rollers 11, and not required to roll synchronously with the lattice 2, the rollers may always be responsive to the small variation of the lattice pitch and its angle.

Further, the expanded structural member of Z type hat type, 2 type, H type, shown in FIGS. 25A and 25B in addition to the channel type and C type as aforementioned may be produced only by changing calibers of rollers in the respective processes.

The differences of the dynamic characteristics between the product of the present invention and the conventional product, and between the product reinforced and the product not reinforced of this invention, are explained in the following Examples.

EXAMPLE 1 Referring now to FIGS. 11A and 11B, FIG. 11A, is an enlarged sectional view of the deformed lattice elements divided into five stages from the example of a central mound shape to the example of a symmetry wavy shape. FIG. 11B is a graph for comparing the results of the strength tests of the deformed lattice element pieces illustrated by No. 2 to No. 6 in FIG. 11A, with the result of the same strength test of the flat lattice element illustrated by No. l in FIG. lllA, the strength test being accomplished with a central concentrate loading method.

The Load-Deflection Diagram shown in FIG. 118 discloses that the means initial rigidity of the reinforcing lattice group is 6 to I6 times larger than that of the flat lattice.

EXAMPLE 2 Both members are produced from the same material.

The above two products are tested by the central concentrate loading method as shown in FIG. 14 and the results are compared by curve (a) for the product of the present invention and curve (12) for the conventional product.

Asseen from the drawing, the maximum load of the present product illustrated in FIGS. 12A and 12B having the lattice angle of 28 is approximately 1.4 times that of the conventional product illustrated in FIGS. 13A and 13B and the stiffness is also larger.

Both of the test pieces used are made by joining a pair of the same products respectively into the box type by means of welding the seams intermittently to each other as shown in FIG. 15.

EXAMPLE 3 The product of the present invention andthe conventional one are shown by the same photograph in FIG. 16.

Even if the conventional product (e) is made from a material having high ductibility such as SPHl (JIS), a crack occurs at the root of the lattice and its lattice angle is as narrow as 24.

On the other hand, the product of this invention (f) ismade from the material of SS4] (JIS) having low ductibility, but no crack occurs at the root of the lattice and with the lattice angle at 35.

EXAMPLE 4 FIG. 17 shows the relationship of the maximum angle of the lattices of the respective products of this invention with respect to the lattice pitch. It is seen therefrom that the products of lattice pitch being 80mm, 75mm, and 70mm have the lattice maximum angle of 27, 30, and 35 respectively.

EXAMPLE Both embodiments shown in FIGS. 18 and 20 are double edged C type expanded structural members which are provided with reinforcement on the lattice element.

FIGS. 19 and 21 are graphs for comparing the results of the strength tests of the products illustrated in FIGS. 18 and 20 with the results of the strength tests of the same products except that their lattice elements are not reinforced, respectively, each test being performed with a central concentrate loading method employing an Amslar testing machine and by 2,000 mm span.

Curve (g) in FIG. 19 shows the strength test result of a product reinforced on its lattice element as shown in FIG. 18, while curve (h) shows that of a product not reinforced thereon.

Curve (1') in FIG. 21 shows the strength test result of a product reinforced on the lattice element shown in FIG. 20, while curve (k) shows that of a product not reinforced thereon.

From the curves in the drawings, it can be clearly understood that the product reinforced on the lattice element at the deflecting point of l/ 300 has approximately 1.5 times as much stiffness as that of the product not reinforced.

The dynamic characteristics of the respective products of the above test results are shown in Table 1.

TABLE 1 Max.

Dynamic Max. Deflection Load of Max. Characterload of max. elastic deflection istics Pmax loading limit of elastic (kg) (mm) P(kg) limit (mm) l I 119 I5 I05 ll.6 2 *2 71.5 15 60 9.8 3 '3 I14 I3 5.8 4 "4 85.5 19 v 50 5.2

Remarks: I

* l )1 product shown in FIG. 18.

"2): the same product as I, but the lattice is not reinforced. *3): product shown in FIG. 20.

*4): the same product as 3, but the lattice is not reinforced.

FIG. 23A is a photograph showing the state of maximum loading during the above strength test of the products shown in FIG. 18. FIG. 23B is a photograph of the same state of the same product shown in FIG. 18 except that it is not reinforced. FIGS. 24A and 24B are similar photographs of the state of the product shown in FIG. 20 and the same product shown in FIG. 20, except that it is not reinforced.

It is understood from the foregoing description that the present invention provides a method and apparatus for manufacturing expanded structural members having superior dynamic characteristics, superior accuracy, various shapes and sizes and various utility with only a rotary motion during cold working without sacrificing productivity. Further, the stiffness of the lattice part of a thin product is increased compared with the size of the shape by working the lattice part without occurrence of cracks'with even 30 or more of lattice angle even for a product have the same hardness and ductibility as those of $541 of Japanese Industrial Standards. This is accomplished by using special dottedly convex rollers to reinforce the lattice part so as to provide various shapes in cold working with high yield and economy.

What is claimed is:

1. An apparatus for manufacturing expanded lattice structural members from blank metal sheet strips by cold working rollers comprising;

slitting rollermeans for providing the web portion with slits, said slitting roller means includes a top and bottom slitting roller, the bottom roller rotating at approximately the speed of themetal strip and means for changingthe speed of the top roller to provide an even lattice pitch to the lattice portion; 

1. An apparatus for manufacturing expanded lattice structural members from blank metal sheet strips by cold working rollers comprising; slitting roller means for providing the web portion with slits, said slitting roller means includes a top and bottom slitting roller, the bottom roller rotating at approximately the speed of the metal strip and means for changing the speed of the top roller to provide an even lattice pitch to the lattice portion; expanding roller means for expanding the web portion in a transverse direction to the movement of the metal strip including pairs of small rollers for generating a compressive force in the longitudinal movement direction of the metal strip, the web portion being expanded into a lattice portion with a degree of slack between pairs of rollers; V-shape expanding roller means for gradually bending the lattice portion into a V-shape; recovering roller means for bending the lattice portion back to a flat position, and levelling roller means for removing the slack to the lattice portion.
 2. An apparatus as in claim 1, where the expanding roller means includes sets of V-shaped rollers which expand the web portion and each set elongates the web portion in a slight excess from that required for the next V-shaped roller set.
 3. An apparatus as in claim 1, where the V-shape expanding roller means includes guiding means for any flange on the metal strip.
 4. An apparatus as in claim 1, further including reinforcing rollers for deforming the lattice portion into having dotted convexities along the surface of the lattice portion.
 5. An apparatus as in claim 4, where the slitting roller means includes a top and bottom slitting roller, the bottom roller rotating at approximately the speed of the metal strip and means for changing the speed of the top roller to provide an even lattice pitch to the lattice portion.
 6. An apparatus as in claim 4, wherein the metal strip has a flange portion formed along the edges thereof, said apparatus further comprising rollers located subsequent to the slitting roller means for expanding the web portion to a lattice angle of at least 25* with respect to the flange portion.
 7. An apparatus as in claim 6, wherein the slitter roller means comprises a C shaped protrusion extending from the circumferential surface thereof for cutting the web portion into a C structural blank, said finishing rolls thEreby extruding a C expanded structural member.
 8. An apparatus as in claim 6, wherein the slitter roller means comprises a Z shaped protrusion extending from the circumferential surface thereof for cutting the web portion into a Z structural blank, said finishing rolls thereby extruding a Z expanded structural member.
 9. An apparatus as in claim 6, wherein the slitter roller means comprises an H shaped protrusion extending from the circumferential surface thereof for cutting the web portion into an H structural blank, said finishing rolls thereby extruding an H expanded structural member.
 10. An apparatus as in claim 6, wherein the slitter roller means comprises a Sigma shaped protrusion extending from the circumferential surface thereof for cutting the web portion into a Sigma structural blank, said finishing rolls thereby extruding a Sigma expanded structural member. 